Switch-mode power supplies (SMPSs) (“power converters”) are widely utilized in consumer, industrial and medical applications to provide well-regulated power while maintaining high power processing efficiency, tight-output voltage regulation, and reduced conducted and radiated electromagnetic interference (EMI).
To meet these conflicting goals, state-of-the-art power converters (flyback converters, forward converters, boost converters, buck converters, and so on) commonly utilize quasi-resonant control methods. Quasi-resonant control methods induce a resonant waveform having sinusoidal voltage oscillations at the drains of one or more semiconductor switches of the power converter. Through well-timed control actions, the semiconductor switches are turned on at the instants where the drain voltage is minimum (i.e., valley switching), thus minimizing the semiconductor switching losses and drain-source dv/dt slope, leading to increased power processing efficiency and reduced electromagnetic interference (EMI).
In some instances, a typical flyback converter may have a slow dynamic response during output load transients and output voltage reference changes. In order to compensate for this slow dynamic response and ensure tight output voltage regulation during load transients, an oversized output capacitor is typically needed, contributing to increased flyback converter cost and volume. Unfortunately, the larger output capacitor capacitance increases the output voltage rise time during output voltage reference changes, potentially affecting output voltage step transition-time compliance in programmable output voltage applications.